Reasons Why Evolution is True Part IX:
DIY Evolution

Although some people may try to refute the theory of evolution, nobody can deny that natural selection occurs. We can demonstrate this quite easily within a single human lifetime, and humans have been inadvertently using natural selection to our own advantage for over 10,000 years. The processes I’m discussing, of course, are artificial selection and domestication.

When Darwin first began to think about evolution, one area of greatest interest to him was domesticated species, in particular the pigeon. The pigeon exists in around 300 of varieties, which have been selected for by pigeon fanciers for at least 5,000 years. The similarities between domestic pigeons and their wild counterparts are clear, however it seems that humans have, over many pigeon generations, been able to shape many aspects of their appearance including plumage colour and shape, body size, and beak shape. Other domesticated species such as dogs, cattle and even crop plants, have undergone significant changes in their appearance and internal anatomy since humans first began breeding them.

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What Makes Us Human Part III
Anatomical Adaptations

When we look at other primates, although the similarities are clear, there are also several stark contrasts. Most noticeable, is our gait – humans are the only truly bipedal (upright walking) primates. Bipedality appeared early in human evolution, and may have marked our divergence from Chimpanzees around 6 million years ago. Bipedality had a number of benefits, allowing us to adapt to a new habitat, and freeing up our hands for other tasks, but compromises also had to be made. Changes in the shape of our pelvis, which enabled us to walk upright, also made childbirth considerably more dangerous and complex. Nevertheless, bipedality is thought to have facilitated the marked advances in tool use and gestural communication that are hallmarks of the human condition.

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How the Beetle Changed its Spots

There is a huge amount of variety in the colours and patterns exhibited by plants and animals. However, most of this variation is fixed at the individual level; only when comparing individuals do we see differences. The ability to change your colour during your lifetime is a trait possessed by only a few animals, which have converged on remarkably similar mechanisms. Colour changes that occur during an animal’s lifetime can occur slowly, with seasonal changes or age (morphological colour change). More dramatically, and more interestingly, some species also have the ability to change their colour or pattern very rapidly, in response to environmental or social conditions (physiological colour change).

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Reasons Why Evolution is True Part VIII:
PreCambrian Rabbits

The fossil record is one of the most obvious pieces of evidence for evolution. Fossils have been known since human history began, and Aristotle first noted the similarity between fossils and living animals, leading him to conclude that fossils represented deceased creatures, a view supported by Leonardo da Vinci. By the 19th century, people were increasingly beginning to appreciate that some fossils represented extinct animals, and that their positioning in the rocks appeared to represent that passage of time. Now there is also ample evidence from molecular genetics and radiometric dating that the fossil record does represent the evolutionary history of life on Earth. Despite this, creationists still continue to argue otherwise. Some have suggested that the fossil record represents animals killed during one or more biblical floods, however this is incongruent with the evidence available.

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What Makes Us Human Part II
Intelligence and Language

One of the most distinctive characteristics of Homo sapiens is our exceptionally large brain, and enhanced cognitive capabilities. In fact, large brains, measured by the encephalisation quotient (EQ), are a characteristic of primates in general, and brain size and complexity has been increasing in the primate lineage for nearly 70 million years. However, this trend is particularly noticeable in the human lineage, and the last 3 million years of hominid evolution have seen the most pronounced increases in encephalisation, with a tripling in brain size. Such a rapid increase in size is extraordinary, especially for an organ so complex. Some areas of the brain have expanded disproportionately, such as the cerebral cortex, which has increased in size by 3 orders of magnitude since our divergence from Chimpanzees. The cerebral cortex accounts for around 85% of total brain volume in humans, and is responsible for complex mental functions.

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Reasons Why Evolution Is True Part VII:
Coevolution

Few species go through life without interacting with an other, but some interactions are more intimate than others. Pollination is an example of an interaction that, in some species, has become very intimate indeed! Most dedicated pollinators show adaptations to this, such as pollen baskets in bees, but these are often generic adaptations that enable the individual to visit many different species of plant. Equally, plants have adaptations to attract a variety of different insects. Different pollinators (bees, birds, moths) have different visual systems, and thus different flower colouration can be used to attract pollinators of different species. The timing of flower and pollinator emergence is also carefully timed in order to ensure maximum cross-over between the two. Pollinators generally gain food from the relationship, whilst plants achieve dispersal of their genes without having to physically move themselves.

Some plant-pollinator interactions are more intimate, more specific. This can lead to more extreme adaptations, as the two species become increasingly specialised for interacting with one another. Possibly the most extreme plant-pollinator relationship exists between the fig and the fig wasp. Young fig wasps emerge as larvae inside a tiny fig. The larvae feed on the fruit of the fig until they are ready to mature into adults, which again occurs within their fig prison. As adults, the wasps mate, collecting pollen from their birth fig before they leave. The male fig wasps then dig their way out of the fruit, creating a path for the females to emerge from. The male fig wasps are not well suited to life outside the fig, however, and often die shortly after making their escape. The females fly off and find a new fig plant where they can lay their eggs. Squeezing through the tiny entrance hole, known as the ostiole, the female enters a new fig and deposits her eggs inside the fruit, simultaneously depositing pollen on the fig’s reproductive parts.

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What Makes Us Human Part I
A Brief History

The earliest known hominid was Sahelanthropus tchadensis, represented only by relatively few fossilised skull fragments, he is so ancient it isn’t clear whether he could truly be considered human at all. Fossils found in Chad, dated to around 7 million years old, may have belonged to a direct human ancestor, or more likely to a neighbouring branch of the ape family tree. This uncertainty is common until around 4 million years ago; many species are known only by partial skeletons and the relationships between them are often unclear. The Australopithecines may be the first group of hominids that we can be said to understand to any extent.

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Reasons Why Evolution is True Part VI:
Homology

Although it makes sense to stick with a good idea when you’ve found it, you wouldn’t stubbornly stick to the same design even when it wasn’t quite working properly, would you? And yet this is just the pattern that appears in nature. Life on Earth shares a remarkable list of features, from protein-handedness and membrane structure to the DNA code. While some of these features, such as protein-handedness (which way around proteins are formed), are inconsequential, others are not. The genetic code is almost completely universal across all life. This is the reason GM can work, because a gene coded for in the genome of one species can be read by the translation machinery in another species’ cells. This does not necessarily have to be true, however, as the code is arbitrary and there are many possible configurations which would work equally well. Furthermore, the code is actually detrimental for some species living in extreme environments, since certain codes are more volatile than others. Despite this, the code is shared by all.

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What Makes Us Human?

Understanding the evolution of Homo sapiens, and how humans came to be human, has been a fascination for people since Darwin’s time, but it has also proved to be one of the most controversial of the sciences. Humans and Chimpanzees diverged about 7 million years ago and during this time a great deal of anatomical and behavioural changes occurred which now distinguish us from our closest relatives. Despite this, we still share over 99% of our genetic make-up with Chimpanzees; only 1% of our genes truly make us human. What is the manifestation of this 1%? Some of these differences are very clear visually; we are taller and less hairy, with larger brains and an upright, two-legged stance. Other differences are slightly more subtle; we have language, we use tools, we have culture and art enabled by abstract thought, we have a concept of self… but as that list continues, it becomes increasingly difficult to determine whether Chimpanzees, or indeed other animals, also share these qualities. If Chimpanzees can be taught language, then this indicates they have a brain capable of understanding and learning language, and thus, surely they can in some sense be said to have language themselves? Other characteristics are even more difficult to pin down; how do you measure self-awareness? Although there is a long list of traits that most people would consider to be exclusively human, the situation is in fact far less clear cut than that.

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Reasons Why Evolution is True

Across the next 10 articles, I present a few of the quirky examples of evolution that we can readily observe in nature. It is by no means an exhaustive list, but merely a set of stories which I feel illustrate well the power of evolution to create complexity, and how we can see evidence for natural selection by looking carefully at the idiosyncrasies it has produced.

The examples I provided in this series can be broadly categorised into a few themes; coevolution (Fig Wasps and Hawk Moths), evolutionary constraints on adaptation (Pandas, The Human Eye), convergent evolution (Birds and Bats), adaptive radiation (Galapagos Finches, Ring Species) and homology (DNA and the Pentadactyl Limb). And within each of these categories, there are numerous other stories I could have told to illustrate my point. But the point I am trying to illustrate is that evolution is a real phenomenon. Charles Darwin’s theory of evolution by natural selection is one which explains the natural world around us in both a satisfying and verifiable way.

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